A good quality of balance is extremely important for turbochargers not only for durability but to reduce unbalance forces that may be transmitted to structures and/or result in turbocharger noise or “whistle”. Most conventional turbochargers include a turbine wheel, a shaft, a compressor wheel and other components that rotate as a group. To balance this group, a combination of component balancing and assembly balancing are typically used. For example, a compressor wheel may be balanced as a component using a balancing spindle and then affixed to a turbocharger shaft and balanced as an assembly.
With respect to assembly balancing, a commonly used practice monitors compressor wheel nose motion in a plane orthogonal to the axis of rotation. However, there can also be significant imbalance in the back plane of the compressor due to misalignment of components on assembly. One of the features that can lead to such misalignment is a locating feature on the turbine shaft and wheel assembly typically referred to as the “stub shaft shoulder”. The stub shaft shoulder acts to locate the compressor wheel and another component, the rotating thrust collar.
When the compressor wheel and the thrust collar are tightened against the stub shaft shoulder, any misalignment with the centerline (axis of rotation) will lead to an offset of the compressor wheel's center of gravity. In turn, an offset in the center of gravity will create imbalance in the back plane area. Consequently, this makes it very difficult to make a single plane correction without building in a “couple imbalance”.
A need exists for technology that facilitates balancing of turbochargers. In particular, a need exists for technology that reduces or eliminates the need for back plane balancing as an assembly. Various exemplary devices, methods, systems, etc., disclosed herein aim to meet these needs and/or other needs.